The present invention relates to a retractable wheel assembly and, more particularly, to a retractable wheel assembly particularly suited for a movable platform or the like that is retractable to stabilize a platform working position.
Large structures such as scaffolding, aerial work platforms, ladder lifts and the like can be made manually movable with the addition of wheels. Caster wheels are particularly suited for such an application due to their multi-directional capabilities. A problem arises, however, when such a movable structure is supported on an inclined surface. Brakes may be added to the wheels to prevent the movable structure from moving, but brakes can wear over time and are subject to failures.
Known structures for moving such items include spring mounted casters and over center casters. Spring mounted casters have an advantage of automatically retracting when loaded, but suffer in that the casters still exert force when the device is loaded, which can make the device less stable when loaded, particularly with occupants at height. Over center mounted casters are either on or off, but do not automatically retract when the device is loaded. Ideally, it would be desirable to provide a device that combines the positive features of the known structures while avoiding the negative features.